CN109970932B - Preparation method and application of micron-sized bifunctional polymer brush immobilized with nitroxide free radicals and sulfonic groups - Google Patents
Preparation method and application of micron-sized bifunctional polymer brush immobilized with nitroxide free radicals and sulfonic groups Download PDFInfo
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Abstract
The invention relates to a micron-sized bifunctional polymer brush for immobilizing nitroxide free radicals and sulfonic groups, which is prepared by taking methacrylic acid-2, 2,6, 6-tetramethyl-4-piperidyl ester TMPM and styrene St as monomers, chloromethylated crosslinked polystyrene microspheres with the particle size of 74-149 mu m and the Cl content of 1.12mmol/g as a macromolecular initiator, synthesizing TMPM and St block copolymer brush by adopting ARGET ATRP, oxidizing the piperidyl of the TMPM into the nitroxide free radicals by using 3-chloroperoxybenzoic acid mCPBA, and sulfonating St by using sulfuric acid. The invention also relates to application of the bifunctional polymer brush in synthesis of active macromonomer of a polycarboxylate superplasticizer. The bifunctional polymer brush prepared by the invention can simultaneously realize the recycling of the polymerization inhibitor and the acid catalyst, reduce the production cost and improve the reaction rate.
Description
Technical Field
The invention belongs to the technical field of nitroxide free radical polymerization inhibitors and sulfonic acid catalysts, and particularly relates to a preparation method of a micron-sized bifunctional polymer brush for immobilizing nitroxide free radicals and sulfonic acid groups and application of the micron-sized bifunctional polymer brush in synthesis of polycarboxylic acid water reducing agent active macromonomers, especially polyethylene glycol monomethyl ether acrylate.
Background
The polycarboxylic acid high-efficiency water reducing agent has a comb-shaped molecular structure, and has attracted attention with excellent performances such as high water reducing rate, low slump loss, low alkali content, good compatibility with cement and the like compared with second-generation naphthalene water reducing agents and melamine water reducing agents. At present, the main technical route for synthesizing the polycarboxylic acid water reducing agent is a direct macromonomer copolymerization method: polyethylene glycol monomethyl ether MPEG and methacrylic acid MAA are used as main raw materials, esterification reaction is firstly carried out to prepare polyethylene glycol monomethyl ether methacrylate MPEGMAA, and then the polyethylene glycol monomethyl ether methacrylate and methacrylic acid are polymerized into the polycarboxylic acid water reducer under the action of an initiator. In the process, the quality of the synthesized functional polyethylene glycol monomethyl ether methacrylate macromonomer with polymerization activity is the key of the good and bad performance of the synthesized polycarboxylic acid water reducing agent.
In the synthesis process of the polyethylene glycol monomethyl ether methacrylate, the reaction temperature is high, and the reaction is required to be carried out at the temperature of 120-130 ℃. Methacrylic acid contains double bonds, so that the activity is high, and the polymerization inhibitor is extremely easy to self-polymerize, so that the addition of the polymerization inhibitor is indispensable. The commonly used high-efficiency polymerization inhibitor is 2,2,6, 6-tetramethyl piperidine nitroxide radical TEMPO, p-tert-butyl catechol TBC, p-methoxyphenol MEHQ and the like. However, these polymerization inhibitors are expensive and remain in the reacted system and are not easy to remove, which affects the curing performance of the product. Esterification reactions generally require catalysts to increase the reaction rate and shorten the reaction time. Strong acids such as p-toluenesulfonic acid and concentrated sulfuric acid are generally selected. Concentrated sulfuric acid has strong oxidizing property, strong corrosivity and strong dehydration property, so that side reactions such as carbonization, oxidation, dehydration, rearrangement and the like are easily caused; the p-toluenesulfonic acid has slow reaction rate and is difficult to recover, so that the performance of the product is influenced. In order to solve the problem of difficult recovery of p-toluenesulfonic acid, macroporous strong acid resin is generally used as a catalyst, but the reaction rate is slow and the esterification rate is low.
In order to solve the problem of recycling the micromolecule polymerization inhibitor, in the patent document CN105820328, a nitrogen-oxygen radical-containing free radical polymer brush PS-PTMA grafted by nano-scale (400-plus-500 nm) crosslinked polystyrene is used as the polymerization inhibitor, p-toluenesulfonic acid is used as an acid catalyst to be applied to the synthesis of the active macromonomer polyethylene glycol monomethyl ether acrylate of the polycarboxylic acid water reducer, the reaction time is 8 h, the polymerization inhibition effect is equivalent to that of the micromolecule polymerization inhibitor, but the p-toluenesulfonic acid is difficult to recycle in the use process.
The matrix of the nitrogenous oxygen radical polymer brush PS-PTMA used in the patent document CN105820328 is a nano-scale crosslinked polystyrene microsphere (400-500 nm), which is prepared by the method described in the patent document CN104162450, expensive raw materials of hydroxyethyl methacrylate and 2-bromoisobutyryl bromide are used, and the 2-bromoisobutyryl bromide has active and dangerous properties, so that the preparation process has great operation difficulty and high cost, and no industrial product exists at present. In addition, the particle size is nano-scale, so the recovery operation difficulty is high and the loss is easy. In order to solve the problem of recycling the polymerization inhibitor and the catalyst at the same time, nitroxide free radicals and sulfonic acid groups are required to be loaded on the same substrate.
The paper "synthesis and catalytic performance of nitroxide radical and sulfonic acid group-containing copolymer" (chemical development, 2018,37 (2), 708-: 2, 2-azobisisobutyronitrile is used as an initiator, sodium styrene sulfonate SSS and methacrylic acid-2, 2,6, 6-tetramethylpiperidinol ester TMPM are used as monomers, and a free radical polymerization method is adopted to prepare the random copolymer P (TMPM-co-SSS). It was then oxidized with 3-chloroperoxybenzoic acid to nitroxide radical containing copolymer P (TMA-co-SSS). Finally, the mixture is acidified by hydrochloric acid to obtain the difunctional copolymer P (TMA-co-HSS) containing nitroxide free radicals and sulfonic acid groups. The copolymer is a linear random copolymer, because the copolymer contains a lipophilic structural unit TMA and a hydrophilic structural unit HSS, the copolymer is not soluble in an oil phase and a water phase, and because a large amount of hydrophilic structural units exist, the copolymer is applied to a reaction system for synthesizing the polyethylene glycol monomethyl ether methacrylate macromonomer of the water reducing agent, the dispersibility is poor, the nitroxide free radical cannot have a polymerization inhibition effect, and the self-polymerization can be caused within 1 hour of the reaction. At present, no technical scheme for simultaneously realizing the recovery of a polymerization inhibitor and an acid catalyst exists.
Disclosure of Invention
In order to solve the problems, the invention provides a preparation method and application of a micron-sized bifunctional polymer brush for immobilizing nitroxide free radicals and sulfonic acid groups.
The invention adopts the following technical scheme: the preparation method comprises the steps of taking methacrylic acid-2, 2,6, 6-tetramethyl-4-piperidyl ester TMPM and styrene St as monomers, chloromethylation crosslinking polystyrene microspheres PS-Cl with the particle size of 74-149 mu m and the Cl content of 1.12mmol/g as a macromolecular initiator, synthesizing the TMPM and St block copolymer brush PS-PSt-PTMPM by adopting an electron transfer activation regeneration catalyst atom transfer radical polymerization ARGET ATRP, oxidizing piperidyl of the TMPM into nitroxide free radicals by using 3-chloroperoxybenzoic acid mCPBA, and sulfonating the St by using sulfuric acid to obtain the micron-sized difunctional polymer brush PS-PSH-PTMA loading the nitroxide free radicals and sulfonic acid groups. The application is that PS-PSH-PTMA with both acid catalysis and free radical trapping replaces a micromolecular acid catalyst and a micromolecular polymerization inhibitor to be used for preparing the active macromonomer polyethylene glycol monomethyl ether acrylate of the polycarboxylate superplasticizer, and the PS-PSH-PTMA is recycled. The preparation route is shown in figure 1.
The preparation method specifically comprises the following steps:
(1) anisole is taken as a reaction medium, under the protection of nitrogen, an electron transfer activation regeneration catalyst atom transfer radical polymerization ARGET ATRP is adopted, chloromethylated polystyrene microspheres PS-Cl with the particle size of 74-149 mu m and the chlorine content of 1.12mmol/g are taken as a macromolecular initiator, styrene St is taken as a monomer, and copper bromide CuBr is taken as2Reacting for 9 hours at 110 ℃ by taking pentamethyldiethylenetriamine PMDETA as a catalyst and stannous octoate as a reducing agent to obtain the polystyrene molecular brush PS-PSt.
(2) Taking anisole as a reaction medium, adopting ARGET ATRP under the protection of nitrogen, taking PS-PSt obtained in the step (1) as a macroinitiator and CuBr2As catalyst, PMDETA as ligand, stannous octoateTMPM is a monomer and reacts for 12h at the temperature of 80 ℃ to obtain the block copolymer of St and TMPM, namely PS-PSt-PTMPM.
(3) Dispersing the PS-PSt-PTMPM in dichloromethane, and oxidizing-NH groups in the PTMPM into nitroxide free radicals with polymerization inhibition by using mCPBA as an oxidizing agent to obtain the nitroxide free radical containing polymer brush PS-PSt-PTMA.
(4) Dispersing the PS-PSt-PTMA obtained in the step (3) in 94% sulfuric acid, and performing sulfonation reaction to obtain the difunctional polymer brush PS-PSH-PTMA immobilized with nitroxide free radicals and sulfonic groups.
In the preparation method, the molar ratio of the materials in the step (1) is CuBr2PMDETA, stannous octoate, PS-Cl, St = 0.1: 1: 100-.
In the preparation method, the molar ratio of the materials in the step (2) is CuBr2PMDETA, stannous octoate, PS-PSt, TMPM = 0.1: 1 (50-200).
In the preparation method, the molar ratio of materials in the step (3) is mCPBA: TMPM = 2:1, and the reaction is carried out for 0.5h at the temperature of 0-5 ℃.
In the preparation method, the molar ratio of the materials in the step (4) is H2SO4St = 50:1, the reaction conditions were 50 ℃ for 6 h.
The application of the bifunctional polymer brush prepared by the method in catalyzing the synthesis of the polycarboxylate superplasticizer macromonomer.
In particular to the application of the bifunctional polymer brush obtained by the preparation method in the synthesis of polyethylene glycol monomethyl ether acrylate by using a catalyst.
Specifically, the synthesis method of the polyethylene glycol monomethyl ether acrylate comprises the following steps: adding methoxypolyethylene glycol, methacrylic acid MAA, an organic solvent and PS-PSH-PTMA into a 250mL four-neck flask with a thermometer, a water separator and a condenser, heating to 120 ℃ by using a constant-temperature oil bath, magnetically stirring, taking out about 1 g of liquid every 1h, titrating by using a potassium hydroxide-absolute ethyl alcohol solution, and determining the esterification rate; after the reaction, filtering, washing with acetone, vacuum drying for 12h, and recovering PS-PSH-PTMA.
Wherein the mol ratio of the sulfonic group, the methoxypolyethylene glycol and the methacrylic acid contained in the PS-PSH-PTMA is 4.23: 4000: 1000.
Wherein the organic solvent is toluene and accounts for 30% of the total mass of the reactants.
The invention has the beneficial effects that: the substrate of the bifunctional polymer brush prepared by the invention is a commercialized micron-sized chloromethylated crosslinked polystyrene microsphere, which is cheap and easy to obtain, has large particle size and is easy to recycle. The bifunctional polymer brush grafted thereto is a block copolymer: one end of a hydrophilic segment PSH containing sulfonic acid groups is grafted on the surface of the micron-sized chloromethylated crosslinked polystyrene microsphere, the other end of the segment PSH containing sulfonic acid groups is connected with a lipophilic segment PTMA containing nitroxide radicals, and in a reaction system for synthesizing the active macromonomer polyethylene glycol monomethyl ether acrylate of the polycarboxylic acid water reducing agent by taking toluene as a reaction medium, the lipophilic segment PTMA can be highly extended to form a micelle-like structure, so that the compatibility with the reaction system is greatly improved. The method of selecting oil-soluble monomer styrene for polymerization and then sulfonation in the preparation of the PSH containing sulfonic acid group chain segment also greatly improves the loading capacity of the sulfonic acid group. Due to the special design of the structure and the preparation process of the polymer brush, the prepared bifunctional polymer brush can simultaneously realize the recycling of the polymerization inhibitor and the acid catalyst, reduce the production cost and improve the reaction rate (which is greatly faster than a micromolecular polymerization inhibitor and acid catalyst system); the purification of the active macromonomer polyethylene glycol monomethyl ether acrylate is facilitated, and the waste liquid amount generated in the purification process is reduced.
Drawings
FIG. 1 is a schematic representation of the preparation process according to the invention.
Detailed Description
The present invention is further described with reference to several embodiments, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention, and the present invention shall be covered thereby.
Example 1
1. Preparation of micron-sized bifunctional polymer brush containing nitroxide free radical and sulfonic group
(1) CuBr was added to a 100mL three-necked flask2(0.0250 g, 0.112 mmol), anisole (30 mL) as solvent and magnetic rotor, and subjecting to ultrasonic oscillation until CuBr is present2After complete dissolution, a condenser and a thermometer were attached to the three-necked flask, and the temperature was set at 40 ℃. St (11.6648 g, 112 mmol), PMDETA (0.23 mL, 1.12 mmol), polystyrene-co-polrvinyl chloride (PS-Cl) (1 g, 1.12 mmol) and stannous octoate (0.36 mL, 1.12 mmol) were added sequentially at 15 min intervals under a nitrogen atmosphere. The reaction temperature was set to 110 ℃ and the reaction was carried out for 9 h. After completion of the reaction, the reaction solution was poured into a beaker. Standing for 12h, filtering to remove supernatant, and vacuum drying to constant weight. The obtained product is the homopolymer brush PS-PSt.
(2) Adding CuBr into a 100mL three-neck flask2(0.0098 g,0.04 mmol), anisole (30 mL) as solvent and a magnetic rotor, and treating CuBr by ultrasonic oscillation2After complete dissolution, a condenser and a thermometer were attached to the three-necked flask, and the temperature was set at 40 ℃. Under a nitrogen atmosphere, TMPM (9.0132 g, 40 mmol), PMDETA (0.084 mL, 0.4 mmol), PS-PSt (1 g, 0.2 mmol) and stannous octoate (0.13 mL, 0.3896 mmol) were added sequentially at 15 min intervals. The reaction temperature was set to 80 ℃ and the reaction was carried out for 12 h. After the reaction is finished, pouring the reaction solution into a beaker, standing for 12h, filtering to remove a supernatant, and drying in vacuum to constant weight. The obtained product is the block copolymer brush PS-PST-PTMPM containing St and TMPM.
(3) A100 mL three-necked flask was charged with PS-PSt-PTMPM (1 g), solvent dichloromethane (20 mL), a magnetic rotor, and a thermometer. Placing the three-neck flask in an ice water bath, slowly dropwise adding a solution prepared from dichloromethane (20 mL) and mCPBA (the molar ratio of mCPBA to TMPM is 2:1) into the reaction solution when the temperature of the reaction system is reduced to be below 0 ℃, and keeping the temperature of the reaction system to be below 5 ℃. After the dropwise addition, the reaction solution is reacted at 0 ℃ for 1h, then the reaction solution is poured into a precipitator n-hexane (300 mL) for precipitation, the obtained product is kept stand for 12h, the supernatant is removed by filtration, and the obtained product is dried in vacuum to constant weight. The obtained product is the block copolymer containing nitroxide radical brush PS-PSt-PTMA.
(4) PS-PSt-PTMA (1 g) and 20 mL of 94% sulfuric acid were added to a 100mL three-necked flask for sulfonation (molar ratio of sulfuric acid to St is 50: 1), stirred vigorously at 50 ℃ for 6 h, washed with distilled water to neutrality, and dried in vacuum to constant weight. The obtained product is the difunctional block copolymer containing nitroxide free radicals and sulfonic groups brush PS-PSH-PTMA (the content of the nitroxide free radicals is 1.34mmol/g, and the content of the sulfonic groups is 5.39 mmol/g).
2. Application of bifunctional polymer brush as polymerization inhibitor and catalyst in synthesis of polycarboxylate superplasticizer active macromonomer polyethylene glycol monomethyl ether acrylate
Adding methoxypolyethylene glycol MPEG into a 250mL four-neck flask with a thermometer, a water separator and a condenser1000(molecular weight: 1000 g/mol) 30 g and 15 mL of toluene, stirring while heating, and waiting for MPEG1000After dissolution, 0.7848g of the bifunctional polymer brush PS-PSH-PTMA (containing 4.23 mmol of sulfonic acid groups and 1.05 mmol of nitroxide free radicals) was added, and then 6.46 g of MAA (MAA and MPEG) methacrylic acid was added dropwise from a constant pressure funnel1000The molar ratio of (1) to (4) —) is determined, the initial acid value of the reaction system is determined by alkali titration after the feeding is finished, the temperature is raised to 120 ℃, the acid value of the reaction system is determined after the constant temperature reaction is carried out for 6 hours, and the esterification rate is calculated to be 99.5%.
After the reaction is finished, filtering and recovering nitroxide free radicals and sulfonic acid group polymer brush PS-PSH-PTMA, washing with acetone, and vacuum drying for 12 h. The recovery rate of the difunctional polymer brush containing the nitroxide free radicals and the sulfonic acid groups is 99.2 percent.
The polymerization inhibiting performance and the catalytic performance of the recovered difunctional polymer brush containing nitroxide free radicals and sulfonic acid groups are investigated according to the steps: the recovery is carried out for 5 times, and the esterification rates of the reaction system are respectively 99.3%, 99.5%, 99.3% and 99.7%.
Example 2
1. Preparation of micron-sized double-tapping functional polymer brush containing nitroxide free radical and sulfonic group
(1) Adding catalyst CuBr into a 100mL three-neck flask2(0.0250 g, 0.112 mmol), anisole (30 mL) as solvent and magnetic rotor, and subjecting to ultrasonic oscillation until CuBr is present2After complete dissolution, the mixture is burnt in three mouthsA condenser tube and a thermometer were attached to the flask, and the temperature was set at 40 ℃. Under a nitrogen atmosphere, monomer St (23.3296 g, 224 mmol), ligand PMDETA (0.23 mL, 1.12 mmol), macroinitiator polystyrene-based chloromethylate PS-Cl (1 g, 1.12 mmol) and reducing agent stannous octoate (0.36 mL, 1.12 mmol) are added in sequence at intervals of 15 min. The reaction temperature was set to 110 ℃ and the reaction was carried out for 9 h. After the reaction, the reaction solution was poured into a beaker, allowed to stand for 12 hours, filtered to remove the supernatant, and vacuum-dried to constant weight. The obtained product is the homopolymer brush PS-PSt.
(2) Adding catalyst CuBr into a 100mL three-neck flask2(0.089 g,0.04 mmol), anisole (30 mL) as solvent and magnetic rotor, ultrasonic vibration until CuBr2After complete dissolution, a condenser and a thermometer were attached to the three-necked flask, and the temperature was set at 40 ℃. Under nitrogen atmosphere, monomer TMPM (4.5066 g, 20 mmol), ligand PMDETA (0.084 mL, 0.4 mmol), macroinitiator PS-PSt (4 g, 0.4 mmol) and reducing agent stannous octoate (0.13 mL, 0.3896 mmol) were added in sequence at intervals of 15 min. The reaction temperature was set to 80 ℃ and the reaction was carried out for 12 h. After the reaction is finished, pouring the reaction solution into a beaker, standing for 12h, filtering to remove a supernatant, and drying in vacuum to constant weight. The obtained product is the block copolymer brush PS-PSt-PTMPM.
(3) A100 mL three-necked flask was charged with PS-PSt-PTMPM (1 g), solvent dichloromethane (20 mL), a magnetic rotor, and a thermometer. Placing the three-neck flask in an ice water bath, slowly dropwise adding a solution prepared from dichloromethane (20 mL) and mCPBA (the molar ratio of mCPBA to TMPM is 2:1) into the reaction solution when the temperature of the reaction system is reduced to be below 0 ℃, and keeping the temperature of the reaction system to be below 5 ℃. After the dropwise addition, the reaction solution is reacted at 0 ℃ for 1h, then the reaction solution is poured into a precipitator n-hexane (300 mL) for precipitation, the obtained product is kept stand for 12h, the supernatant is removed by filtration, and the obtained product is dried in vacuum to constant weight. The obtained product is the block copolymer containing nitroxide radical brush PS-PSt-PTMA.
(4) PS-PSt-PTMA (1 g) and 20 mL of 94% sulfuric acid were added to a 100mL three-necked flask for sulfonation (molar ratio of sulfuric acid to St is 50: 1), stirred vigorously at 50 ℃ for 6 h, washed with distilled water to neutrality, and dried in vacuum to constant weight. The obtained product is the difunctional block copolymer containing nitroxide free radicals and sulfonic groups brush PS-PSH-PTMA (the content of the nitroxide free radicals is 1.70 mmol/g, and the content of the sulfonic groups is 3.55 mmol/g).
2. Application of bifunctional polymer brush as polymerization inhibitor and catalyst in synthesis of polycarboxylate superplasticizer active macromonomer polyethylene glycol monomethyl ether acrylate
Adding methoxypolyethylene glycol MPEG into a 250mL four-neck flask with a thermometer, a water separator and a condenser1000(molecular weight: 1000 g/mol) 30 g and 15 mL of toluene, stirring while heating, and waiting for MPEG1000After dissolution, 1.1915g of the bifunctional polymer brush PS-PSH-PTMA (containing 4.23 mmol of sulfonic acid groups and 2.03 mmol of nitroxide free radicals) was added, and then 6.46 g of MAA (MAA and MPEG) methacrylic acid was added dropwise from a constant pressure funnel1000The molar ratio of the components is 4: 1) and 0.0312 g of micromolecule 2,2,6, 6-tetramethylpiperidine-1-oxygen free radical mixture, after the feeding is finished, alkali titration is carried out to determine the initial acid value of the reaction system, the temperature is increased to 120 ℃, after 5 hours of constant temperature reaction, the acid value of the reaction system is determined, and the esterification rate is calculated to be 99.8%.
After the reaction is finished, filtering and recovering nitroxide free radicals and sulfonic acid group polymer brush PS-PSH-PTMA, washing with acetone, and vacuum drying for 12 h. The recovery rate of the difunctional polymer brush containing the nitroxide free radicals and the sulfonic acid groups is 99.5 percent.
The polymerization inhibiting performance and the catalytic performance of the recovered difunctional polymer brush containing nitroxide free radicals and sulfonic acid groups are investigated according to the steps: the recovery is carried out for 5 times, and the esterification rates of the reaction system are respectively 99.1%, 99.5%, 99.6%, 99.3% and 99.2%.
Comparative example 1
Adding methoxypolyethylene glycol MPEG into a 250mL four-neck flask with a thermometer, a water separator and a condenser1000(molecular weight: 1000 g/mol) 30 g and 15 mL of toluene, stirring while heating, and waiting for MPEG1000After dissolution, 6.46 g MAA (MAA and MPEG) methacrylate was added dropwise from a constant pressure funnel1000In a molar ratio of 4: 1) and 0.1291 g of small molecules of a mixture of 2,2,6, 6-tetramethylpiperidine-1-oxyl TEMPO (0.83 mmol), the feed being terminated and the reverse being determined by base titrationAccording to the initial acid value of the system, 0.7291 g of p-toluenesulfonic acid (4.23 mmol) is added, the temperature is raised to 120 ℃, the acid value of the reaction system is measured after the reaction is carried out for 10 hours at constant temperature, and the esterification rate is calculated to be 98.2%.
Comparative example 2
Adding methoxypolyethylene glycol MPEG into a 250mL four-neck flask with a thermometer, a water separator and a condenser1000(molecular weight: 1000 g/mol) 30 g and 15 mL of toluene, stirring while heating, and waiting for MPEG1000After dissolution, 1.0552g of bifunctional random copolymer P (TMA-co-HSS) (containing 4.23 mmol of sulfonic acid group and 2.03 mmol of nitroxide radical) were added, and then 6.46 g of methacrylic acid MAA (MAA and MPEG) were added dropwise from a constant pressure funnel1000The molar ratio of (1) to (4) in the reaction system, carrying out alkali titration after the feeding is finished, measuring the initial acid value of the reaction system, heating to 120 ℃, reacting at constant temperature for 1h, and then carrying out self-polymerization.
In the comparative example, the 2,2,6, 6-tetramethylpiperidine-1-oxyl polymerization inhibitor and the p-toluenesulfonic acid catalyst used were dissolved in the reaction system and were difficult to recover, resulting in waste.
In the above examples 1-2, the catalyst and the polymerization inhibitor used were micron-sized bifunctional polymer brushes. One end of a linear polymer chain containing nitroxide free radicals and sulfonic structural units in the polymer brush is bonded on the surface of the insoluble micron-sized crosslinked polystyrene microsphere through a covalent bond, and the other end of the linear polymer chain can be freely stretched in a reaction system. From the examples 1-2, it can be seen that the polystyrene-based bifunctional polymer brush has good polymerization inhibition performance and catalytic performance after being recycled for 5 times, and the esterification rate of the synthesized product is over 99%.
Claims (8)
1. A preparation method of a micron-sized bifunctional polymer brush immobilized with nitroxide free radicals and sulfonic acid groups is characterized by comprising the following steps:
(1) anisole is used as a reaction medium and is protected by nitrogenAdopting an electron transfer activation regeneration catalyst atom transfer free radical polymerization ARGET ATRP, using chloromethylation polystyrene microsphere PS-Cl with the grain diameter of 74-149 mu m and the chlorine content of 1.12mmol/g as a macroinitiator, using styrene St as a monomer, and using copper bromide CuBr2Reacting for 9 hours at 110 ℃ by taking pentamethyldiethylenetriamine PMDETA as a catalyst and stannous octoate as a reducing agent to obtain polystyrene molecular brush PS-PSt;
(2) taking anisole as a reaction medium, adopting an ARGET ATRP method under the protection of nitrogen, taking PS-PSt obtained in the step (1) as a macroinitiator and CuBr2Taking PMDETA as a catalyst, taking stannous octoate as a reducing agent, taking methacrylic acid-2, 2,6, 6-tetramethyl-4-piperidyl ester TMPM as a monomer, and reacting for 12 hours at 80 ℃ to obtain a block copolymer of St and TMPM, namely PS-PSt-PTPM;
(3) dispersing the PS-PSt-PTMPM in dichloromethane, and oxidizing-NH groups in TMPM into nitroxide free radicals with polymerization inhibition by using 3-chloroperoxybenzoic acid mCPBA as an oxidizing agent to obtain a nitroxide free radical polymer brush PS-PSt-PTMA;
(4) dispersing the PS-PSt-PTMA obtained in the step (3) in 94 percent of sulfuric acid H2SO4And carrying out sulfonation reaction to obtain the difunctional polymer brush PS-PSH-PTMA with the nitrogen-oxygen free radicals and the sulfonic groups immobilized.
2. The method according to claim 1, wherein the molar ratio of each material in step (1) is CuBr2PMDETA, stannous octoate, PS-Cl, St = 0.1: 1: 100-.
3. The method according to claim 1, wherein the molar ratio of each material in the step (2) is CuBr2PMDETA, stannous octoate, PS-PSt, TMPM = 0.1: 1 (50-200).
4. The application of the micron-sized bifunctional polymer brush with the nitrogen-oxygen radical and the sulfonic acid radical immobilized prepared according to any one of claims 1 to 3 in synthesis of polycarboxylic acid water reducer macromonomers.
5. The use of claim 4, wherein the polycarboxylate water reducer macromonomer is polyethylene glycol monomethyl ether acrylate.
6. The application of claim 5, wherein the synthesis method of the polyethylene glycol monomethyl ether acrylate is as follows: adding methoxy polyethylene glycol, methacrylic acid MAA, an organic solvent and PS-PSH-PTMA into a 250mL four-neck flask with a thermometer, a water separator and a condenser, heating to 120 ℃ by using a constant-temperature oil bath, magnetically stirring, taking out 1 g of liquid every 1h, titrating by using a potassium hydroxide-absolute ethyl alcohol solution, and determining the esterification rate; after the reaction, filtering, washing with acetone, vacuum drying for 12h, and recovering PS-PSH-PTMA.
7. The use according to claim 6, wherein the PS-PSH-PTMA contains sulfonic acid groups, methoxypolyethylene glycol and methacrylic acid in a molar ratio of 4.23: 4000: 1000.
8. The use according to claim 6, wherein the organic solvent is toluene and represents 30% of the total mass of the reactants.
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| CN103242495A (en) * | 2012-12-27 | 2013-08-14 | 苏州大学 | Method for preparing diblock copolymer containing polyamide chain segments |
| CN104162450A (en) * | 2013-05-16 | 2014-11-26 | 河北科技大学 | Preparation method for polymer brush supported TEMPO catalyst system |
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| CN103242495A (en) * | 2012-12-27 | 2013-08-14 | 苏州大学 | Method for preparing diblock copolymer containing polyamide chain segments |
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